A seafloor experiment designed to monitor deep-sea vents
turned into the perfect tool for gauging the amount of oil that escaped the
Macondo Well into the Gulf of Mexico during the Deepwater Horizon disaster.

Researchers looked at almost all the high-resolution video
of the spewing oil released by BP and the government. They then applied their
technique to assess the oil's billowy movement in short clips and estimate the
volume of oil
that leaked out.

Their analysis shows that the Deepwater Horizon disaster
easily topped the Exxon Valdez tanker spill by
releasing more than 10 times the amount of oil into the Gulf. It also found
that an earlier spill estimate of just 5,000 barrels of oil per day was 10
times less than the actual flow rate.

"This is a
great example of how basic research that doesn't seem to have any immediate
value suddenly gains huge immediacy for society," said study researcher Timothy
Crone, a marine geophysicist at Columbia University, in a statement.

Crone and his
colleague, Maya Tolstoy, had first developed the optical plume velocimetry
technique to analyze underwater camera footage of deep-sea vents in the
offshore waters near the U.S. Pacific Northwest.

But they became go-to
experts for estimating the true oil spill rates in May, after it became clear
that the 5,000 barrels-per-day estimate was a lowball figure.

How to gauge a gusher

The researchers
based their new estimates on two 20- to 30-second video clips, one taken before
the removal of a damaged riser pipe on June 3 and the other after.

Their technique
calculated the flow rate of the billowing oil by using an estimate of image
resolution to get a flow rate in meters per video frame, and then applying a
frame rate estimate of time to convert the flow rate into meters per second.

Additional
calculations eventually led to an estimated flow rate in barrels of oil spilled per day, Crone explained in an e-mail. The full
study is detailed in the Sept. 23 online edition of the journal Science.

Crone and Tolstoy estimate that 56,000 barrels per day flowed
into the Gulf waters from the broken riser pipe between April 22 and June 3,
starting from the date when the oil rig exploded and sank.

Removal of the oil well's riser pipe then allowed 68,000 barrels
of oil to spill forth each day, until BP finally sealed the well on July 15.

Getting it right for
the future

One big limit for
the technique is that it requires high-resolution video, unlike the low-resolution
video footage made public during the long months following the initial oil rig
explosion. That's why the researchers were limited to the few high-resolution
clips they did analyze.

More high-resolution
video could help reduce the uncertainties for the current estimates using this
technique, Crone said. The uncertainties currently stand at 21 percent for the
56,000-barrels-per-day estimate, and 19 percent for the 68,000-barrels-per-day-estimate.

"I do not know
if any additional video is available," Crone told LiveScience. "If it
is, I would be quite interested in evaluating it."

The estimated 4.4 million barrels of oil that spewed uncollected
into the Gulf easily makes the Deepwater Horizon disaster one of the worst
oil spills in history. Only the Persian Gulf War oil spill would top that
amount with an estimated 8.8 million barrels.

An "oily
snow" mix of degraded oil and organic material has already begun to
coat the seafloor. Now researchers are scrambling to figure out the long-term
effects.

Jeremy Hsu

Jeremy has written for publications such as Popular Science, Scientific American Mind and Reader's Digest Asia. He obtained his masters degree in science journalism from New York University, and completed his undergraduate education in the history and sociology of science at the University of Pennsylvania.